I have a modular home on a vented crawl space. There is a concrete foundation with vents in the concrete around the outside of the house and concrete piers with steal posts supporting the rest of the house. The perimeter  foundation walls are 4 feet tall. The dirt floor inside the concrete foundation is actually at the same level as the bottom of the concrete footing  supporting the foundation walls. The dirt floor is covered with plastic sheets for a moisture barrier and has worked well. The ceiling of the crawl space is currently insulated with fiberglass sheets. 

The problem is that the area above the insulation below the floor is an ideal gathering place for field mice here in the northern Denver area on our farm. The house is about 25 years old and the floor insulation is covered with mouse droppings and urine. 
I want to take out the insulation and dispose of it  to eliminate the smell.
I then want to use spray foam insulate it.

The house is a triple wide. Each section 13 feet wide and about 70 feet long. Each section is on two steel beams. Each has a full length heat duct running the length of the house with floor vents above the fiberglass insulation. There are PEX plumbing pipes for cold and hot water above the fiberglass insulation too. The drain pipes go strait down where needed/created above the ceiling and and then run below the fiberglass insulation.  The Floor joists rest on the beams. I realize this is a big job. The large kits of spray foam like Tiger Foam TF-600FR would take 5 kits for approximately 3000 SQ Feet and cost 5 x $750.  I am willing to do this work. That’s not the issue.

What I wonder is about the pros and cons.  And are there things I need to do to insure success?